A Highly Selective NIR Fluorescent Turn-on Probe for Hydroxyl Radical and Its Application in Living Cell Images

Mid-IR Light-Activatable Full Spectrum LaB6 Plasmonic Photocatalyst

Photocatalysts as long-lasting, benign reagents for disinfection of bacteria in hospitals and public areas/facilities/transportation vehicles are strongly needed. A common limitation for all existing semiconductor photocatalysts is the requirement of activation by external UV-vis-near-infrared (NIR) light with wavelengths shorter than ≈1265 nm. None of the existing photocatalysts can function during nighttime in the absence of external light. Herein, an unprecedented LaB6 plasmonic photocatalyst is reported, which can absorb UV-vis-NIR light and mid-IR (3900 nm) light to split water and generate hydrogen and hydroxyl radicals for the decomposition of organic pollutants, as well as kill multidrug-resistant Escherichia coli bacteria. Mid-IR light (≈2-50 µm) is readily available from the natural environments via thermal radiation of warm/hot objects on the earth including human bodies, animals, furnances, hot/warm electrical devices, and buildings.

Reactive oxygen species in biological media are they friend or foe? Major In vivo and In vitro sensing challenges

The role of Reactive Oxygen Species (ROS) on biological media has been shifting over the years, as the knowledge on the complex mechanism that lies in underneath their production and overall results has been growing. It has been known for some time that these species are associated with a number of health conditions. However, they also participate in the immunoactivation cascade process, and can have an active role in theranostics. Macrophages, for example, react to the presence of pathogens through ROS production, potentially allowing the development of new therapeutic strategies. However, their short lifetime and limited spatial distribution of ROS have been limiting factors to the development and understanding of this phenomenon. Even though, ROS have shown successful theranostic applications, e.g., photodynamic therapy, their wide applicability has been hampered by the lack of effective tools for monitoring these processes in real time. Thus the development of innovative sensing strategies for in vivo monitoring of the balance between ROS concentration and the resultant immune response is of the utmost relevance. Such knowledge could lead to major breakthroughs towards the development of more effective treatments for neurodegenerative diseases. Within this review we will present the current understanding on the interaction mechanisms of ROS with biological systems and their overall effect. Additionally, the most promising sensing tools developed so far, for both in vivo and in vitro tracking will be presented along with their main limitations and advantages. This review focuses on the four main ROS that have been studied these are: singlet oxygen species, hydrogen peroxide, hydroxyl radical and superoxide anion.

Cell Uptake of Steroid-BODIPY Conjugates and Their Internalization Mechanisms: Cancer Theranostic Dyes

Estradiol-BODIPY linked via an 8-carbon spacer chain and 19-nortestosterone- and testosterone-BODIPY linked via an ethynyl spacer group were evaluated for cell uptake in the breast cancer cell lines MCF-7 and MDA-MB-231 and prostate cancer cell lines PC-3 and LNCaP, as well as in normal dermal fibroblasts, using fluorescence microscopy. The highest level of internalization was observed with 11β-OMe-estradiol-BODIPY 2 and 7α-Me-19-nortestosterone-BODIPY 4 towards cells expressing their specific receptors. Blocking experiments showed changes in non-specific cell uptake in the cancer and normal cells, which likely reflect differences in the lipophilicity of the conjugates. The internalization of the conjugates was shown to be an energy-dependent process that is likely mediated by clathrin- and caveolae-endocytosis. Studies using 2D co-cultures of cancer cells and normal fibroblasts showed that the conjugates are more selective towards cancer cells. Cell viability assays showed that the conjugates are non-toxic for cancer and/or normal cells. Visible light irradiation of cells incubated with estradiol-BODIPYs 1 and 2 and 7α-Me-19-nortestosterone-BODIPY 4 induced cell death, suggesting their potential for use as PDT agents.

Rhodol-Based Fluorescent Probes Used for Fast Response toward ClO– and Delayed Determination of H2O2 in Living Cells

Reactive oxygen species (ROS), a class of reactive oxidants, play critical roles in signal transduction, cell metabolism, immune defense, and other physiological processes. Abnormally excessive levels of ROS can cause diseases and thus, investigations into the relevant biology and medicine are significant. The behavior of ROS in inflammation has been rarely elucidated. In this work, two ROS fluorescent probes, FS-ROS1 and FS-ROS2 have been designed and synthesized. FS-ROS1 responds rapidly (~1 min) to ClO– and gradually (~30 min) to H2O2 with an increase in fluorescence at ~656 nm and 640 nm of more than 100-fold in vitro. At a concentration of 10 μM, FS-ROS1 labels the L929 cell and Raw264.7 cell wells in 30 min with excellent biocompatibility and without washing. After labelling, FS-ROS1 exhibited a rational fluorescence increase upon the addition of 1, 10, 100, and 200 μM of H2O2. Based on these results, inflammatory cells, stimulated with 800 nM dexamethasone and polyIC, showed a higher increase in fluorescence than the control cells. These results suggest that H2O2 and ClO– might be important signaling molecules during inflammations.

BODIPY derivatives as fluorescent reporters of molecular activities in living cells

Fluorescent compounds have become indispensable tools for imaging molecular activities in the living cell. 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) is currently one of the most popular fluorescent reporters due to its unique photophysical properties. This review provides a general survey and presents a summary of recent advances in the development of new BODIPY-based cellular biomarkers and biosensors. The review starts with the consideration of the properties of BODIPY derivatives required for their application as cellular reporters. Then review provides examples of the design of sensors for different biologically important molecules, ions, membrane potential, temperature and viscosity defining the live cell status. Special attention is payed to BODPY-based phototransformable reporters.

The bibliography includes 339 references.

Intriguing Heteroleptic ZnII bis(dipyrrinato) Emitters in the Far-Red Region With Large Pseudo-Stokes Shift for Bioimaging

Novel heteroleptic ZnII bis(dipyrrinato) complexes were prepared as intriguing emitters. With our tailor-made design, we achieved far-red emissive complexes with a photoluminescence quantum yield up to 45% in dimethylsulfoxide and 70% in toluene. This means that heteroleptic ZnII bis(dipyrrinato) complexes retain very intense emission also in polar solvents, in contrast to their homoleptic counterparts, which we prepared for comparing the photophysical properties. It is evident from the absorption and excitation spectra that heteroleptic complexes present the characteristic features of both ligands: the plain dipyrrin (Lp) and the π-extended dipyrrin (Lπ). On the contrary, the emission comes exclusively from the π-extended dipyrrin Lπ, suggesting an interligand nonradiative transition that causes a large pseudo-Stokes shift (up to 4,600 cm-1). The large pseudo-Stokes shifts and the emissive spectral region of these novel heteroleptic ZnII bis(dipyrrinato) complexes are of great interest for bioimaging applications. Thus, their high biocompatibiliy with four different cell lines make them appealing as new fluorophores for cell imaging.

A sensitive BODIPY-based fluorescent probe for detecting endogenous hydroxyl radicals in living cells

A novel “turn-on” NIR fluorescent probe was designed and used for monitoring endogenous hydroxyl radical in living cells, which also showed higher selectivity toward hydroxyl radical over other reactive oxygen/nitrogen species.